Process of treating cellulose and derivatives thereof



Patented Nov. 10, 1936 UNITED STATES PATENT OFFICE PROCESS OF TREATING CELLULOSE AND DERIVATIVES THEREOF poration of Delaware No Drawing. Application September 4, 1934, Serial No. 742,694

11 Claims.

This invention relates to the art of retarding deterioration of organic materials and more particularly to the stabilizing of cellulose, cellulose manufactures, and chemical derivatives of cellulose.

It has been discovered that deterioration of the above materials can be effectively retarded by treating them with small amounts of certain stabilizing chemical agents, namely, esters and N-substituted esters of carbamic, thiocarbamic, thiolcarbamic, and dithiocarbamic acids.

The deterioration of cellulosic substances, such as those with which the present invention is concerned, seems to be induced or accelerated by light, particularly ultraviolet light. In other words the deterioration seems in many instances to be photochemical since its rapidity frequently varies directly with the intensity of the light and with the concentration of ultraviolet light. However, as is well known, cellulosic bodies also deteriorate, though more slowly, in ordinary sunlight (direct or difiused) and in the absence of light, under atmospheric conditions. In the absence of light, this deterioration is often very slow and imperceptible except over long periods of time but takes place nevertheless as evidenced by the discoloration and weakening of paper, books, cotton fabrics, newspaper files, etc., even when stored in dark places at comparatively low temperatures. Thus, while the rate of deterioration may vary with the particular conditions, the present agents will be found effective for retarding it under any given set of conditions. However, neither the nature of the deterioration of cellulosic substances (whether hydrolytic, oxidative, or otherwise) nor the manner in which the present agents function to prevent it, is definitely known, and it is not desired to be confined to any theory thereof.

The general object of this invention is thus to provide methods for retarding the deleterious effects of aging on paper, cellulosic fabrics, and various other cellulosic materials.

A particular object of this invention is to provide methods of decreasing the deterioration, due to or initiated by ultraviolet rays and other causes, of those cellulosic substances included in the group consisting of regenerated cellulose, cellulose ethers, and organic acid esters of cellulose. These materials may be in the form of fibres,

yarns, fabrics, and sheets of different sizes, shapes, and transparency. Examples of cellulose esters with which the present agents may be used effectively are cellulose acetate, cellulose butyrate, cellulose laurate, cellulose isobutyrate, cellulose propionate, cellulose crotonate, etc. Examples of cellulose ethers are methyl cellulose, ethyl cellulose, benzyl cellulose, dodecyl cellulose, crotyl cellulose, cinnamyl cellulose, glycol cellulose, and cellulose glycollic acid. The cellulose esters and ethers may be of the highor low-substituted type, having, for example, from one substituent group for each eight glucose units up to three substituent groups for each glucose unit.

Another particular object of this invention is to provide methods of retarding the deteriorating effect of aging on various cellulose manufactures included in a group comprising paper, cotton filaments, and woven and knitted fabrics of cotton, linen, ramie, jute, etc.

Other objects and advantages of the invention will be pointed out in the following description or will be apparent from such description.

These objects are accomplished by treating paper, cotton goods, and the other aforementioned cellulosic materials with the mentioned chemical agents, which have the property of stabilizing the cellulosic materials against the injurious effect of aging, whether or not accompanied by exposure to concentrated ultraviolet rays.

The agents employed in this invention may be represented by the general formula where X1 and X: are oxygen or sulfur, R1 is a monovalent hydrocarbon radical, and R2 and R3 are hydrogen or monovalent organic (especially hydrocarbon) radicals. R1, R2, and R3, for example, may be such general types of hydrocarbon radicals as alkyl, alkenyl, aryl, aralkyl, cycloalkyl, etc., or such particular hydrocarbon radicals as methyl, ethyl, propyl, i-butyl, amyl, decyl, dodecyl, octadecyl, phenyl, tolyl, xylyl, naphthyl, benzyl, cinnamyl, 9,10-octadecenyl, cyclohexyl, naphthenyl, etc.

esters of carbamic, thiocarbamic,

' Methyl dithiocarbamate thiolcarbamic and dithiocarbamic acids, salts and N-substituted salts of these acids may be used, e. g; the ammonium, sodium, potassium, calcium, barium, etc., salts. R1 of the general formula then becomes a metal. Salts are less suitable in this invention, however, because of their instability.

The most effective agents of this invention are the esters and N-substituted esters of carbamic and thiocarbamic acids as exemplified by the following. Most of these compounds are also called urethanes and thiourethanes:

Esters and N-substituted esters of carbamzc acid (NH zCOOH N-phenyl ethyl cerbamate N-tolyl ethyl carbamate N-u-naphthyl ethyl carbamate N -phenyl methoxyethyl cerbamate N -phenyl methyl carbemate N-phenyl crotyl carbamate N-phenyl dodecyl carbamate N-a-naphthyl dodecyl carbamate N-phenyl naphthenyl carbamates N-acetyl ethyl carbamate N-methyl ethyl carbamate N-hydroxymethyl ethyl earbamate CH=(NHCOOO1H5); C1H OCOGH(NHCOC H); N-methyl- -phenyl ethyl carbamate Methyl carbamate Ethyl carbamate I-amyl curbamate Dodecyl carbamate Cmtyl carbamate 9, ltl-octadecyl carbamste Phenyl cerbamate Tolyl carbametes aand fl'naphthyl carbamates Cyclohexyl carbamate N aphthenyl earbamates Ethoxyethyl carbamate Esters and N-substituted esters of thiocarbamz'c' acid (NHzCSOH) N-ethyl ethyl thiocarbamate- N-allyl ethyl thiocarbamate N-acetyl methyl thiocarbamate N-phenyl ethyl thiocarbamate N -phenyl cellulose thioearbamate N-a-naphthyl dodecyl thlccarbamate N-phe nyl ethoxyethyl thiocarbsma e N-phenyl naphthenyl thiocarhamates Ethyl thiocarbamate I-butyl thiocarbamate Phenyl thiocarbamate Tetraacetyl glucose thiocarbamate Other compounds which are useful and included in this invention are the following:

Esters and N-substituted esters of thiolcarbamic acid (NHzCOSH) Methyl thiolcerbamate Ethyl thiolcarbamate Phenyl thiolcarbamete Dodecyl thiolcarbamate N-ethyl ethyl thiolcarbamate N-phenyl ethyl thiolearbamate N-pheuyl phenyl thiolcarbamate N-B-naphthyl dodecyl thiolcarbamate Methoxyethyl thiolcarba- N-phenyl naphthenyl thlolcarbamate mate Allyl thiolcarbamate N-phenyl oleyl thlolcarbamate Esters and N-substituted esters of dithtocarbamic acid (NHzC'SSH) N-dimethyl methyl dithlocarbamate N -methyl methyl dithiocarbamate N-acetyl ethyl dithiocarbamate N-phenyl ethyl dithiocarbamate N-a-nephthyl dodecyl dithiocarbamate dlthiocarba- N-phenyl naphthenyl dithiocarbamates Isopropyl dithiocarbamate Allyl dithiocarbamate Phenyl dithioearbumate lDodecyl dithiocarbamate Example 1 This example illustrates the treatment of viscose rayonwith an ester of thiocarbamic acid. Strips of woven viscose rayon fabric one-half inch wide were immersed for one hour in a 5% alcoholic solution of N-phenyl ethyl thiocarba mate (phenyl thiourethane). The excess liquid was squeezed out and the treated strips kept side by side with untreated control strips of exactly the same size and shape for 24 hours at 25 C. and 50% relative humidity. Two of the controls and two of the treated strips were then tested for elongation and breaking strength on a Scott testing machine. The values obtained-approximately the same for both-were taken as 100%. All the remaining strips, together with the remaining controls, were then exposed to ultraviolet rays under a Cooper-Hewitt quartz mercuryvapor lamp in order to accelerate the deterioration of the fabric. All strips were placed at a distance of approximately 24 inches from the lamp where the temperature was approximately 30 C. Exposure was continued for 72 hours, two control strips and two treated strips being removed at the end of 36 and 72 hours, then stored at 25 C. and 50% relative humidity for 24 hours, and finally tested for elongation and breaking strength in the same manner as before exposure. At the end of 36 hours the untreated control had retained 51.6% and the treated fabric 58.5% of the original strength. At the end of 72 hours these values were 28.3% and 48.8% respectively. By this time the untreated control was quite weak, readily torn, and practically useless, but the treated fabric, while definitely weakened, was still usable.

Ethyl thiocarbamate, N-acetyl methyl thiocarbamate N-ethyl ethyl thiocarbamate, etc., may be used in the above example instead of phenylthiourethane and good results obtained in retarding the weakening, discoloration, and general deterioration of the fabric. These agents are also effective with cellulose acetate, cotton, and paper. While they may be used in the raw material, they-are more conveniently and effectively applied to some manufacture thereof, as acetate rayon (fibers or fabrics), thin transparent sheets of regenerated cellulose such as those ordinarily used for wrapping purposes, cotton or rayon textiles, rope, threads, etc.

As previously pointed out, these agents are also effective when the treated base material is subjected to light of difierent types and intensities,

and/or when aged in the absence of light, the' ultraviolet light merely being used for quick results.

Example 2 This example illustrates the use of an ester of carbamic acid.

Woven viscose rayon fabric is treated with a 5% aqueous solution of ethyl carbamate (urethane) in the same manner as in Example 1. After 36 hours exposure to ultraviolet light under the same conditions as in Example 1, the fabric retained 66.6% of its original strength while the untreated control retained only 51.6%. The corresponding figures at the end of 72 hours were 47.6% and 28.3%. Urethane is a particularly desirable agent because it may be used in aqueous solutions without sacrifice of eifectiveness.

In the above example, the ethyl carbamate may be replaced by methyl carbamate, phenyl carbamate, ethoxyethyl carbamate, etc. and good results obtained. However, appropriate lowboiling solvents which do not attack the base material should be used in applying the agent. Paper, paper pulp, cotton, and cellulose derivatives may also be rendered more resistant to deterioration by treatment with these agents after the general manner of Example 2.

Example 3 This example illustrates the use of an N-subituted ester of carbamic acid.

Woven viscose rayon fabric was soaked in a alcoholic solution of N-phenyl ethyl carunate (phenylurethane) and the treated fabric posed to ultraviolet light together with uneated controls. After 36 hours the treated fabc possessed 63.0% of its original strength, and 1e control only 51.6%. After 72 hours, these gures were 54.8% and 28.3% respectively.

It will be seen from the above examples that ripregnated samples of fabric show marked imrovement over the untreated samples in their :sistance to deterioration as induced or accel- 'ated by. ultraviolet light, particularlyafterthe nger period of test. 1

All the systems in which these agents are used, hether cellulose, a cellulosic manufacture, or a zllulose ether or ester or a manufacture therepossess the common feature of a more or less we number of substituted or unsubstituted glu- 188 units or building stones joined together. It believed that upon aging this structure is afected in some way, and that the agents menoned herein critically prevent such degradation r deterioration.

As many apparently widely. different embodnents of this invention may be made without aparting from the spirit and scope thereof, it is v be understood that we do not limit ourselves I the specific embodiments thereof except as e-fined in the appended claims.

We claim:

'1. The process of rendering cellulosic fibres and orous manufactures thereof more resistant to re deleterious effects of aging which consists in ipregnating them with a small percentage of 1 agent having the general formula 1 which X1 and X2 are oxygen or sulfur, R1 is monovalent hydrocarbon radical, and R2 and R3 re hydrogen or monovalent organic radicals.

2. The process of rendering cellulosic fibres ad fibrous manufactures thereof more resistant 1 the deleterious effects of aging which consists 1 impregnating them with 0.25% to 5.0% of an gent of the formula herein X1 and X: are oxygen or sulfur, R1 is a lonovalent hydrocarbon radical, and R2 and R: re hydrogen or monovalent organic radicals.

3. The process of rendering paper more restant to the deleterious effects of aging, by imregnating it with 0.25% to 5.0% of an agent of 1e formula iRl herein X1 and X: are oxygen or sulfur, R1 is a monovalent hydrocarbon radical, and R2 and R: are hydrogen or monovalent organic radicals.

4. The process of rendering cotton and fabricated cotton more resistant to the deleterious effects of aging by impregnating them with 0.25% to 5.0% of an agent of the formula wherein X1 and K2 are oxygen or sulfur, R1 is a monovalent hydrocarbon radical, and R: andR: are hydrogen or monovalent organic radicals.

5. The process of rendering viscose filaments and fabrics more resistant to the deleterious effects of aging byimpregnatlng them with 0.25% to 5.0% of an agent of the formula wherein X1 and X2 are oxygen or sulfur, R1 is a monovalent hydrocarbon radical, and R: and Rs are hydrogen or monovalent organic radicals.

6. Celluloslc fibres and fibrous manufactures thereof impregnated with a compound represented by the general formula in which X1 and & are oxygen or sulfur, R1 is a monovalent hydrocarbon radical, and R2 and R3 are hydrogen or a monovalent organic radical. 7. Cellulosic fibres and fibrous manufactures thereof impregnated with 0.25% to 5.0% of a compound of the general formula csx wherein X1 and X: are oxygen or sulfur, R1 is a monovalent hydrocarbon radical and R: and R3 are hydrogen or monovalent organic radicals.

8. Cellulosic threads, and fabrics impregnated with 0.25% to 5.0% of a compound of the formula wherein X1 and X1 are oxygen or sulfur, R1 is a monovalent hydrocarbon radical and R: and R: impregnated with 0.25% to 5.0% of a compoum are hydrogen or mo'novalent organic radicals. of the formula v 10. Cotton and fabricated cotton impregnated xm with 0.25% to 5.0% of a. compound of the formula 0 x 5 v wherein x1 and x: are oxygen or sulfur. R1 is i 10 r monovalent hydrocarbon radical and R2 and R wherein-X; and, X: are oxygen or sulfur, R1 is a are hydrogen or monovalent organic radicals.

monovalent hydrocarbon radical and R2 and Rs are hydrogen or monovalent organic radicals. JAMES KARR HUNT.

' 11. Regenerated cellulose filaments and fabrics GEORGE HENRY LA 

